The human transcription factor protein p53 induces cell cycle arrest and apoptosis in response to DNA damage and cellular stress, and thereby plays a critical role in protecting cells from malignant transformation. The E3 ubiquitin ligase HDM2 negatively regulates p53 function through a direct binding interaction that neutralizes the p53 transactivation activity, leads to export from the nucleus of p53 protein, and targets p53 for degradation via the ubiquitylation-proteasomal pathway. Loss of p53 activity, either by deletion, mutation, or HDM2 overexpression, is the most common defect in human cancers. Tumors that express wild type p53 are vulnerable to pharmacologic agents that stabilize or increase the concentration of active p53. In this context, inhibition of the activities of HDM2 has emerged as a validated approach to restore p53 activity and resensitize cancer cells to apoptosis in vitro and in vivo. HDMX (HDM4) has more recently been identified as a similar negative regulator of p53, and studies have revealed significant structural homology between the p53 binding interfaces of HDM2 and HDMX.
The p53-HDM2 and p53-HDMX protein-protein interactions are mediated by the same 15-residue alpha-helical transactivation domain of p53, which inserts into hydrophobic clefts on the surface of HDM2 and HDMX. Three residues within this domain of p53 (F19, W23, and L26) are essential for binding to HDM2 and HDMX. The present invention provides p53-based peptidomimetic macrocycles that modulate the activities of p53 by inhibiting the interactions between p53 and HDM2, p53 and HDMX, or p53 and both HDM2 and HDMX proteins, and that may be used for treating diseases including but not limited to cancer and other hyperproliferative diseases.